Manifold system having flow control

ABSTRACT

An injection molding apparatus and method are provided in which the rate of material flow during an injection cycle is controlled. According to one preferred embodiment, an injection molding apparatus is provided that includes a manifold, at least one injection nozzle coupled to the manifold, an actuator, and a valve pin adapted to reciprocate through the manifold and the injection nozzle. The valve pin has a first end coupled to the actuator, a second end that closes the gate in a forward position, and a control surface intermediate said first and second ends for adjusting the rate of material flow during an injection cycle. Retracting the valve pin tends to decrease the rate of material flow during the injection cycle and displacing the valve pin toward the gate tends to increase the rate of material flow during the injection cycle.

RELATED APPLICATIONS

This application is a Continuation-in-Part under 35 U.S.C. §120 of U.S.application Ser. No. 09/063,762, entitled “MANIFOLD SYSTEM HAVING FLOWCONTROL”, filed Apr. 21, 1998 now U.S. Pat. No. 6,361,300, and claimspriority under 35 U.S.C. §119(e) to Provisional Application Ser. No.60/124,596, entitled “DYNAMIC FEED VALVE GATE”, filed Mar. 16, 1999.

FIELD OF THE INVENTION

This invention relates to injection of pressurized materials through amanifold, such as injection molding of plastic melt in a hot runnersystem. More specifically, this invention relates to an improvedinjection molding hot runner system in which the rate of melt flow iscontrolled through the gate during an injection molding cycle.

DESCRIPTION OF THE RELATED ART

U.S. Pat. No. 5,556,582 discloses a multi-gate single cavity system inwhich the rate of melt flow through the individual gates is controlledindependently via a control system according to specific target processconditions. This system enables the weld line of the part (the sectionof the part in which the melt from one gate meets the melt from anothergate) to be selectively located. It also enables the shape of the weldline to be altered to form a stronger bond.

The '582 patent discloses controlling the rate of melt flow with atapered valve pin at the gate to the mold cavity. It also disclosesplacing a pressure transducer inside the mold cavity. Placing thepressure transducer inside the mold cavity can result in the pressuretransducer sensing pressure spikes which can occur when the valve pin isclosed. A pressure spike sensed by the transducer can cause anunintended response from the control system, and result in a lessprecise control of the melt flow than desired.

The control system disclosed in the '582 patent uses the variables ofvalve pin position and cavity pressure to determine what position thevalve pin should be in. Thus, the algorithm performed by the controlsystem in the '582 patent utilizes two variables to control the rate ofmelt flow into the cavity.

SUMMARY OF THE INVENTION

An injection molding apparatus and method are provided in which the rateof material flow during an injection cycle is controlled. According toone preferred embodiment, an injection molding apparatus is providedthat includes a manifold, at least one injection nozzle coupled to themanifold, an actuator, and a valve pin adapted to reciprocate throughthe manifold and the injection nozzle. The valve pin has a first endcoupled to the actuator, a second end that closes the gate in a forwardposition, and a control surface intermediate said first and second endsfor adjusting the rate of material flow during an injection cycle.Retracting the valve pin tends to decrease the rate of material flowduring the injection cycle and displacing the valve pin toward the gatetends to increase the rate of material flow during the injection cycle.

According to another preferred embodiment, in an injection moldingsystem having a manifold for injecting material into first and secondmold cavities, respectively, and a controller for controlling the flowrate of material injected into the first and second mold cavities duringan injection cycle according to first and second target profiles,respectively, wherein the first and second target profiles represent adesired value of first and second sensed conditions related to the flowrate of material injected into the first and second cavities during aninjection cycle, respectively, a method is provided for creating atleast the first target profile for the first mold cavity. The methodincludes the steps of shutting off a flow of material into the secondcavity, and injecting material into the first cavity to determine whatvalues of the first sensed condition produce an acceptable molded partin the first cavity, the values of the first sensed condition thatproduce an acceptable molded part constituting the first target profile.

According to another preferred embodiment, in an injection moldingsystem having a manifold for injecting material into first and secondmold cavities, respectively, and a controller for controlling the flowrate of material injected into the first and second mold cavitiesaccording to first and second target profiles, respectively, whereineach target profile represents a desired value of first and secondsensed conditions related to the flow rate of material injected into thefirst and second cavities during an injection cycle, respectively, amethod is provided for creating the first and second target profiles.The method includes the step of simultaneously injecting material intothe first and second cavities; and based on the simultaneous injectionof material, determining what values of the first sensed conditionproduce an acceptable molded part in the first mold cavity, the valuesof the first sensed condition that produce an acceptable molded partconstituting the first target profile, and determining what values ofthe second sensed condition produce an acceptable molded part in thesecond mold cavity, the values of the second sensed condition thatproduce an acceptable molded part in the second mold cavity constitutingthe second target profile.

According to another preferred embodiment, in an injection moldingsystem having a manifold for injecting material through first and secondgates into one or more mold cavities, and a controller for controllingthe flow rate of material injected through the first and second gatesduring an injection cycle according to first and second target profiles,respectively, wherein the first and second target profiles represent adesired value of first and second sensed conditions related to the flowrate of material injected through the first and second gates during aninjection cycle, respectively, a method is provided for creating atleast the first target profile, the method includes the steps ofselecting a test first target profile to be executed by the controller,injecting material through the first gate into a cavity according to thetest first target profile executed by the controller, and determiningwhether the material injected produces an acceptable molded part in thecavity.

According to another preferred embodiment, in an injection moldingsystem having a manifold for injecting material through a first gateinto a first mold cavity, and a controller for controlling the flow rateof material injected through the first gate during an injection cycleaccording to a first target pressure profile by comparing a targetpressure to an actual pressure during the injection cycle, wherein thefirst target pressure profile represents a target value of the pressureexerted by the material injected through the first gate during theinjection cycle, a method is provided for creating the first targetpressure profile. The method includes the steps of selecting a value ofa variable corresponding to target injection pressure of the injectedmaterial, selecting a value of a variable corresponding to target packpressure of the injected material, and selecting a value of a variablecorresponding to a duration of the injection cycle.

According to another preferred embodiment, in an injection moldingsystem having a manifold for injecting material through a first gateinto a first mold cavity, and a controller for controlling the flow rateof material injected through the first gate during an injection cycleaccording to a first target pressure profile by comparing a targetpressure to an actual pressure exerted by the material, a method isprovided for creating the first target pressure profile. The methodincludes selecting pressure values for a plurality of variablescorresponding to target pressures at a corresponding plurality of timesduring the injection cycle, and forming the first target pressureprofile according to the pressure values.

According to another preferred embodiment, an injection moldingapparatus is provided that includes a manifold for directing materialthrough first and second gates into one or more mold cavities, and acontroller to independently control a flow rate of material injectedinto through the first and second gates during an injection cycleaccording to a first target profile associated with the materialinjected through the first gate and a second target profile associatedwith material injected through the second gate. The first target profilerepresents target values of a first sensed condition related to the flowrate of material injected through the first gate during the injectioncycle and the second target profile represents target values of a secondsensed condition related to the flow rate of material injected throughthe second gate during the injection cycle. The apparatus furtherincludes a graphical user interface for displaying at least the firsttarget profile.

According to another preferred embodiment, an injection moldingapparatus is provided that includes a manifold to direct material tofirst and second gates into one or more mold cavities, the manifoldincluding first and second wells associated with each gate, a first ramto force material from the first well through the first gate, a secondram to force material from the second well through the second gate, anda controller to independently control first and second rates at whichthe first and second rams force material through the first and secondgates and into the one or more mold cavities during an injection cycle.

According to another preferred embodiment, an injection moldingapparatus is provided that includes a manifold to direct material into amold cavity, a valve pin adapted to reciprocate through the manifoldtoward and away from the mold cavity, wherein valve pin contactsmaterial injected into the mold cavity, and a controller to control aflow rate of material injected into the first cavity during an injectioncycle based on a force exerted on the valve pin by the material.

According to another preferred embodiment, in an injection moldingsystem apparatus having a manifold, at least one injection nozzlecoupled to the manifold, an actuator, and a valve pin adapted toreciprocate through the manifold and the injection nozzle, the valve pinhaving a first end coupled to the actuator, and a second end that closesthe gate, a method is provided having the steps of prior to thebeginning of an injection cycle, placing the valve pin in a rearwardposition, moving the valve pin forward from the rearward position at thebeginning of the injection cycle toward the gate to an intermediateposition in which material flow is permitted, and moving the valve pinfurther toward the gate from the intermediate position to close the gateat the end of the injection cycle.

According to another preferred embodiment, in an injection moldingsystem having a manifold to direct material to first and second gates,the manifold including first and second wells associated with each gate,a method is provided including the steps of injecting material into eachof the first and second wells, injecting material from the each of thefirst and second wells through each of the first and second gates, andindependently controlling the rates at which the material is injectedfrom the first and second wells.

According to another preferred embodiment, in an injection moldingsystem having a manifold to direct material to first and second gateswhich lead to one or more mold cavities, the first and second gateshaving first and second valve pin associated therewith, a method isprovided having the steps of injecting material into the manifold,determining a first force exerted by the material on the first valvepin, and a second force exerted by the material on the second valve pin,respectively, and independently controlling the rate at which thematerial is injected through each of the first and second gates into theone or more mold cavities based on the first and second forces,respectively.

According to another preferred embodiment, in an injection moldingsystem having a manifold to direct material to first and second gateswhich lead to one or more mold cavities, a method is provided thatincludes the steps of injecting material into the manifold, controllingin the manifold a first rate at which material is injected through thefirst gate into the one or more mold cavities based on a first pressuresensed in the one or more cavities, and controlling in the manifold asecond rate at which material is injected through the second gate intothe one or more mold cavities based on a second pressure sensed in theone or more cavities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially schematic cross-sectional view of an injectionmolding system according to one embodiment of the present invention;

FIG. 2 is an enlarged fragmentary cross-sectional view of one side ofthe injection molding system of FIG. 1;

FIG. 3 is an enlarged fragmentary cross-sectional view of an alternativeembodiment of a system similar to FIG. 1, in which a plug is used foreasy removal of the valve pin;

FIG. 4 is an enlarged fragmentary cross-sectional view of an alternativeembodiment of a system similar to FIG. 1, in which a threaded nozzle isused;

FIG. 5 is a view similar to FIG. 4, showing an alternative embodiment inwhich a plug is used for easy removal of the valve pin;

FIG. 6 shows a fragmentary cross-sectional view of a system similar toFIG. 1, showing an alternative embodiment in which a forward shut-off isused;

FIG. 7 shows an enlarged fragmentary view of the embodiment of FIG. 6,showing the valve pin in the open and closed positions, respectively;

FIG. 8 is a cross-sectional view of an alternative embodiment of thepresent invention similar to FIG. 6, in which a threaded nozzle is usedwith a plug for easy removal of the valve pin;

FIG. 9 is an enlarged fragmentary view of the embodiment of FIG. 8, inwhich the valve pin is shown in the open and closed positions;

FIG. 10 is an enlarged view of an alternative embodiment of the valvepin, shown in the closed position;

FIG. 11 is a fragmentary cross sectional view of an alternativeembodiment of an injection molding system having flow control thatincludes a valve pin that extends to the gate;

FIG. 12 is an enlarged fragmentary cross-sectional detail of the flowcontrol area;

FIG. 13 is a fragmentary cross sectional view of another alternativeembodiment of an injection molding system having flow control thatincludes a valve pin that extends to the gate, showing the valve pin inthe starting position prior to the beginning of an injection cycle;

FIG. 14 is view of the injection molding system of FIG. 13, showing thevalve pin in an intermediate position in which material flow ispermitted;

FIG. 15 is a view of the injection molding system of FIG. 13, showingthe valve pin in the closed position at the end of an injection cycle;and

FIG. 16 shows a series of graphs representing the actual pressure versusthe target pressure measured in four injection nozzles coupled to amanifold as shown in FIG. 13;

FIGS. 17 and 18 are screen icons displayed on interface 114 of FIG. 13which are used to display, create, edit, and store target profiles;

FIG. 19 is a fragmentary cross-sectional partially schematic view ofanother alternative embodiment of an injection molding system havingflow control in which a ram is used to inject material from a well inthe manifold into the mold cavity;

FIG. 20 is a fragmentary view of the embodiment shown in FIG. 19 inwhich the well 640 is being filled by the injecting molding machine;

FIG. 21 is a view similar to FIG. 20 in which the well is full ofmaterial and the system is ready to inject material into the moldcavity;

FIG. 22 is a view similar to FIGS. 20 and 21 in which injection into themold cavity has begun;

FIG. 23 is a view similar to FIGS. 20-22 in which the injection cycle iscomplete;

FIG. 24 is a cross-sectional partially schematic view of anotheralternative embodiment of an injection molding system having flowcontrol in which a load cell behind the valve pin is used to control theflow rate in each injection nozzle;

FIG. 25 is a enlarged fragmentary cross-sectional view of the valve pinand actuator of FIG. 24;

FIG. 26 is an enlarged view of the load cell and valve pin of FIG. 24;

FIGS. 27A and 27B show an enlarged view of the tip of the valve pinclosing the gate and controlling the flow rate, respectively;

FIGS. 28A and 28B shown an alternative structure of an injection moldingnozzle for use in the system shown in FIG. 24;

FIG. 29 is a cross-sectional partially schematic view of an alternativeembodiment of an injection molding system having flow control similar toFIG. 19 in which a pressure transducer is used to sense the hydraulicpressure supplied to the actuator;

FIG. 30 shows a fragmentary cross-sectional view of an alternativeembodiment of an injection molding system having flow control similar toFIG. 13 in which the pressure transducer is mounted in the mold cavity;and

FIG. 31 is a fragmentary cross-sectional view of an alternativeembodiment of an injection molding system having flow control in whichflow control is effected by measuring the differential pressure of theactuator chambers.

DETAILED DESCRIPTION

FIGS. 1-2 show one embodiment of the injection molding system accordingto the present invention. The injection molding system 1 is a multi-gatesingle cavity system in which melt material 3 is injected into a cavity5 from gates 7 and 9. Melt material 3 is injected from an injectionmolding machine 11 through an extended inlet 13 and into a manifold 15.Manifold 15 distributes the melt through channels 17 and 19. Although ahot runner system is shown in which plastic melt is injected, theinvention is applicable to other types of injection systems in which itis useful to control the rate at which a material (e.g., metallic orcomposite materials) is delivered to a cavity.

Melt is distributed by the manifold through channels 17 and 19 and intobores 18 and 20 of nozzles 21 and 23, respectively. Melt is injected outof nozzles 21 and 23 and into cavity 5 (where the part is formed) whichis formed by mold plates 25 and 27. Although a multi-gate single-cavitysystem is shown, the invention is not limited to this type of system,and is also applicable to, for example, multi-cavity systems, asdiscussed in greater detail below.

The injection nozzles 21 and 23 are received in respective wells 28 and29 formed in the mold plate 27. The nozzles 21 and 23 are each seated insupport rings 31 and 33. The support rings serve to align the nozzleswith the gates 7 and 9 and insulate the nozzles from the mold. Themanifold 15 sits atop the rear end of the nozzles and maintains sealingcontact with the nozzles via compression forces exerted on the assemblyby clamps (not shown) of the injection molding machine. An O-ring 36 isprovided to prevent melt leakage between the nozzles and the manifold. Adowel 73 centers the manifold on the mold plate 27. Dowels 32 and 34prevent the nozzle 23 and support ring 33, respectively, from rotatingwith respect to the mold 27.

The nozzles also include a heater 35 (FIG. 2). Although an electric bandheater is shown, other heaters may be used. Furthermore, heat pipes (forexample those disclosed in U.S. Pat. No. 4,389,002) may be disposed ineach nozzle and used alone or in conjunction with heater 35. The heateris used to maintain the melt material at its processing temperature upto the gates 7 and 9. The nozzles 21 and 23 also include an insert 37and a tip 39. The insert can be made of a material (for exampleberyllium copper) having high thermal conductivity in order to maintainthe melt at its processing temperature up to the gate by imparting heatto the melt from the heater 35. The tip 39 is used to form a seal withthe mold plate 27 and is preferably a material (for example titaniumalloy or stainless steel) having low thermal conductivity so as toreduce heat transfer from the nozzle to the mold.

A valve pin 41 having a head 43 is used to control the rate of flow ofthe melt material to the respective gates 7 and 9. The valve pinreciprocates through the manifold. A valve pin bushing 44 is provided toprevent melt from leaking along stem 102 of the valve pin. The valve pinbushing is held in place by a threadably mounted cap 46. The valve pinis opened at the beginning of the injection cycle and closed at the endof the cycle. During the cycle, the valve pin can assume intermediatepositions between the fully open and closed positions, in order todecrease or increase the rate of flow of the melt. The head includes atapered portion 45 that forms a gap 81 with a surface 47 of the bore 19of the manifold. Increasing or decreasing the size of the gap bydisplacing the valve pin correspondingly increases or decreases the flowof melt material to the gate. When the valve pin is closed the taperedportion 45 of the valve pin head contacts and seals with the surface 47of the bore of the manifold.

FIG. 2 shows the head of the valve pin in a Phantom dashed line in theclosed position and a solid line in the fully opened position in whichthe melt is permitted to flow at a maximum rate. To reduce the flow ofmelt, the pin is retracted away from the gate by an actuator 49, tothereby decrease the width of the gap 81 between the valve pin and thebore 19 of the manifold.

The actuator 49 (for example, the type disclosed in application Ser. No.08/874,962) is mounted in a clamp plate 51 which covers the injectionmolding system 1. The actuator 49 is a hydraulic actuator, however,pneumatic or electronic actuators can be used. The actuator 49 includesa hydraulic circuit that includes a movable piston 53 in which the valvepin 41 is threadably mounted at 55. Thus, as the piston 53 moves, thevalve pin 41 moves with it. The actuator 49 includes hydraulic lines 57and 59 which are controlled by servo valves 1 and 2. Hydraulic line 57is energized to move the valve pin 41 toward the gate to the openposition, and hydraulic line 59 is energized to retract the valve pinaway from the gate toward the close position. An actuator cap 61 limitslongitudinal movement in the vertical direction of the piston 53.O-rings 63 provide respective seals to prevent hydraulic fluid fromleaking out of the actuator. The actuator body 65 is mounted to themanifold via screws 67.

A pressure transducer 69 is used to sense the pressure in the manifoldbore 19 downstream of the valve pin head 43. In operation, theconditions sensed by the pressure transducer 69 associated with eachnozzle are fed back to a control system that includes controllers PID 1and PID 2 and a CPU shown schematically in FIG. 1. The CPU executes aPID (proportional, integral, derivative) algorithm which compares thesensed pressure (at a given time) from the pressure transducer to aprogrammed target pressure (for the given time). The CPU instructs thePID controller to adjust the valve pin using the actuator 49 in order tomirror the target pressure for that given time. In this way a programmedtarget pressure profile for an injection cycle for a particular part foreach gate 7 and 9 can be followed.

Although in the disclosed embodiment the sensed condition is pressure,other sensed conditions can be used which relate to melt flow rate. Forexample, the position of the valve pin or the load on the valve pincould be the sensed condition. If so, a position sensor or load sensor,respectively, could be used to feed back the sensed condition to the PIDcontroller. In the same manner as explained above, the CPU would use aPID algorithm to compare the sensed condition to a programmed targetposition profile or load profile for the particular gate to the moldcavity, and adjust the valve pin accordingly.

Melt flow rate is directly related to the pressure sensed in bore 19.Thus, using the controllers PID 1 and PID 2, the rate at which the meltflows into the gates 7 and 9 can be adjusted during a given injectionmolding cycle, according to the desired pressure profile. The pressure(and rate of melt flow) is decreased by retracting the valve pin anddecreasing the width of the gap 81 between the valve pin and themanifold bore, while the pressure (and rate of melt flow) is increasedby displacing the valve pin toward the gate 9, and increasing the widthof the gap 81. The PID controllers adjust the position of the actuatorpiston 51 by sending instructions to servo valves 1 and 2.

By controlling the pressure in a single cavity system (as shown inFIG. 1) it is possible to adjust the location and shape of the weld lineformed when melt flow 75 from gate 7 meets melt flow 77 from gate 9 asdisclosed in U.S. Pat. No. 5,556,582. However, the invention also isuseful in a multi-cavity system. In a multi-cavity system the inventioncan be used to balance fill rates and packing profiles in the respectivecavities. This is useful, for example, when molding a plurality of likeparts in different cavities. In such a system, to achieve a uniformityin the parts, the fill rates and packing profiles of the cavities shouldbe as close to identical as possible. Using the same programmed pressureprofile for each nozzle, unpredictable fill rate variations from cavityto cavity are overcome, and consistently uniform parts are produced fromeach cavity.

Another advantage of the present invention is seen in a multi-cavitysystem in which the nozzles are injecting into cavities which formdifferent sized parts that require different fill rates and packingprofiles. In this case, different pressure profiles can be programmedfor each respective controller of each respective cavity. Still anotheradvantage is when the size of the cavity is constantly changing, i.e.,when making different size parts by changing a mold insert in which thepart is formed. Rather than change the hardware (e.g., the nozzle)involved in order to change the fill rate and packing profile for thenew part, a new program is chosen by the user corresponding to the newpart to be formed.

The embodiment of FIGS. 1 and 2 has the advantage of controlling therate of melt flow away from the gate inside manifold 15 rather than atthe gates 7 and 9. Controlling the melt flow away from the gate enablesthe pressure transducer to be located away from the gate (in FIGS. 1-5).In this way, the pressure transducer does not have to be placed insidethe mold cavity, and is not susceptible to pressure spikes which canoccur when the pressure transducer is located in the mold cavity or nearthe gate. Pressure spikes in the mold cavity result from the valve pinbeing closed at the gate. This pressure spike could cause an unintendedresponse from the control system, for example, an opening of the valvepin to reduce the pressure—when the valve pin should be closed.

Avoidance of the effects of a pressure spike resulting from closing thegate to the mold makes the control system behave more accurately andpredictably. Controlling flow away from the gate enables accuratecontrol using only a single sensed condition (e.g., pressure) as avariable. The '582 patent disclosed the use of two sensed conditions(valve position and pressure) to compensate for an unintended responsefrom the pressure spike. Sensing two conditions resulted in a morecomplex control algorithm (which used two variables) and morecomplicated hardware (pressure and position sensors).

Another advantage of controlling the melt flow away from the gate is theuse of a larger valve pin head 43 than would be used if the valve pinclosed at the gate. A larger valve pin head can be used because it isdisposed in the manifold in which the melt flow bore 19 can be madelarger to accommodate the larger valve pin head. It is generallyundesirable to accommodate a large size valve pin head in the gate areawithin the end of the nozzle 23, tip 39 and insert 37. This is becausethe increased size of the nozzle, tip and insert in the gate area couldinterfere with the construction of the mold, for example, the placementof water lines within the mold which are preferably located close to thegate. Thus, a larger valve pin head can be accommodated away from thegate.

The use of a larger valve pin head enables the use of a larger surface45 on the valve pin head and a larger surface 47 on the bore to form thecontrol gap 81. The more “control” surface (45 and 47) and the longerthe “control” gap (81)—the more precise control of the melt flow rateand pressure can be obtained because the rate of change of melt flow permovement of the valve pin is less. In FIGS. 1-3 the size of the gap andthe rate of melt flow is adjusted by adjusting the width of the gap,however, adjusting the size of the gap and the rate of material flow canalso be accomplished by changing the length of the gap, i.e., the longerthe gap the more flow is restricted. Thus, changing the size of the gapand controlling the rate of material flow can be accomplished bychanging the length or width of the gap.

The valve pin head includes a middle section 83 and a forward coneshaped section 95 which tapers from the middle section to a point 85.This shape assists in facilitating uniform melt flow when the melt flowspast the control gap 81. The shape of the valve pin also helpseliminates dead spots in the melt flow downstream of the gap 81.

FIG. 3 shows another aspect in which a plug 87 is inserted in themanifold 15 and held in place by a cap 89. A dowel 86 keeps the plugfrom rotating in the recess of the manifold that the plug is mounted.The plug enables easy removal of the valve pin 41 without disassemblingthe manifold, nozzles and mold. When the plug is removed from themanifold, the valve pin can be pulled out of the manifold where the plugwas seated since the diameter of the recess in the manifold that theplug was in is greater than the diameter of the valve pin head at itswidest point. Thus, the valve pin can be easily replaced withoutsignificant downtime.

FIGS. 4 and 5 show additional alternative embodiments of the inventionin which a threaded nozzle style is used instead of a support ringnozzle style. In the threaded nozzle style, the nozzle 23 is threadeddirectly into manifold 15 via threads 91. Also, a coil heater 93 is usedinstead of the band heater shown in FIGS. 1-3. The threaded nozzle styleis advantageous in that it permits removal of the manifold and nozzles(21 and 23) as a unitary element. There is also less of a possibility ofmelt leakage where the nozzle is threaded on the manifold. The supportring style (FIGS. 1-3) is advantageous in that one does not need to waitfor the manifold to cool in order to separate the manifold from thenozzles. FIG. 5 also shows the use of the plug 87 for convenient removalof valve pin 41.

FIGS. 6-10 show an alternative embodiment of the invention in which a“forward” shutoff is used rather than a retracted shutoff as shown inFIGS. 1-5. In the embodiment of FIGS. 6 and 7, the forward cone-shapedtapered portion 95 of the valve pin head 43 is used to control the flowof melt with surface 97 of the inner bore 20 of nozzle 23. An advantageof this arrangement is that the valve pin stem 102 does not restrict theflow of melt as in FIGS. 1-5. As seen in FIGS. 1-5, the clearance 100between the stem 102 and the bore 19 of the manifold is not as great asthe clearance 100 in FIGS. 6 and 7. The increased clearance 100 in FIGS.6-7 results in a lesser pressure drop and less shear on the plastic.

In FIGS. 6 and 7 the control gap 98 is formed by the front cone-shapedportion 95 and the surface 97 of the bore 20 of the rear end of thenozzle 23. The pressure transducer 69 is located downstream of thecontrol gap—thus, in FIGS. 6 and 7, the nozzle is machined toaccommodate the pressure transducer as opposed to the pressuretransducer being mounted in the manifold as in FIGS. 1-5.

FIG. 7 shows the valve pin in solid lines in the open position andPhantom dashed lines in the closed position. To restrict the melt flowand thereby reduce the melt pressure, the valve pin is moved forwardfrom the open position towards surface 97 of the bore 20 of the nozzlewhich reduces the width of the control gap 98. To increase the flow ofmelt the valve pin is retracted to increase the size of the gap 98.

The rear 45 of the valve pin head 43 remains tapered at an angle fromthe stem 102 of the valve pin 41. Although the surface 45 performs nosealing function in this embodiment, it is still tapered from the stemto facilitate even melt flow and reduce dead spots.

As in FIGS. 1-5, pressure readings are fed back to the control system(CPU and PID controller), which can accordingly adjust the position ofthe valve pin 41 to follow a target pressure profile. The forwardshut-off arrangement shown in FIGS. 6 and 7 also has the advantages ofthe embodiment shown in FIGS. 1-5 in that a large valve pin head 43 isused to create a long control gap 98 and a large control surface 97. Asstated above, a longer control gap and greater control surface providesmore precise control of the pressure and melt flow rate.

FIGS. 8 and 9 show a forward shutoff arrangement similar to FIGS. 6 and7, but instead of shutting off at the rear of the nozzle 23, theshut-off is located in the manifold at surface 101. Thus, in theembodiment shown in FIGS. 8 and 9, a conventional threaded nozzle 23 maybe used with a manifold 15, since the manifold is machined toaccommodate the pressure transducer 69 as in FIGS. 1-5. A spacer 88 isprovided to insulate the manifold from the mold. This embodiment alsoincludes a plug 87 for easy removal of the valve pin head 43.

FIG. 10 shows an alternative embodiment of the invention in which aforward shutoff valve pin head is shown as used in FIGS. 6-9. However,in this embodiment, the forward cone-shaped taper 95 on the valve pinincludes a raised section 103 and a recessed section 104. Ridge 105shows where the raised portion begins and the recessed section ends.Thus, a gap 107 remains between the bore 20 of the nozzle through whichthe melt flows and the surface of the valve pin head when the valve pinis in the closed position. Thus, a much smaller surface 109 is used toseal and close the valve pin. The gap 107 has the advantage in that itassists opening of the valve pin which is subjected to a substantialforce F from the melt when the injection machine begins an injectioncycle. When injection begins melt will flow into gap 107 and provide aforce component F1 that assists the actuator in retracting and openingthe valve pin. Thus, a smaller actuator, or the same actuator with lesshydraulic pressure applied, can be used because it does not need togenerate as much force in retracting the valve pin. Further, the stressforces on the head of the valve pin are reduced.

Despite the fact that the gap 107 performs no sealing function, itswidth is small enough to act as a control gap when the valve pin is openand correspondingly adjust the melt flow pressure with precision as inthe embodiments of FIGS. 1-9.

FIGS. 11 and 12 show an alternative hot-runner system having flowcontrol in which the control of melt flow is still away from the gate asin previous embodiments. Use of the pressure transducer 69 and PIDcontrol system is the same as in previous embodiments. In thisembodiment, however, the valve pin 41 extends past the area of flowcontrol via extension 110 to the gate. The valve pin is shown in solidlines in the fully open position and in Phantom dashed lines in theclosed position. In addition to the flow control advantages away fromthe gate described above, the extended valve pin has the advantage ofshutting off flow at the gate with a tapered end 112 of the valve pin41.

Extending the valve pin to close the gate has several advantages. First,it shortens injection cycle time. In previous embodiments thermal gatingis used. In thermal gating, plastication does not begin until the partfrom the previous cycle is ejected from the cavity. This preventsmaterial from exiting the gate when the part is being ejected. Whenusing a valve pin, however, plastication can be performed simultaneouslywith the opening of the mold when the valve pin is closed, thusshortening cycle time by beginning plastication sooner. Using a valvepin can also result in a smoother gate surface on the part.

The flow control area is shown enlarged in FIG. 12. In solid lines thevalve pin is shown in the fully open position in which maximum melt flowis permitted. The valve pin includes a convex surface 114 that tapersfrom edge 128 of the stem 102 of the valve pin 41 to a throat area 116of reduced diameter. From throat area 116, the valve pin expands indiameter in section 118 to the extension 110 which extends in a uniformdiameter to the tapered end of the valve pin.

In the flow control area the manifold includes a first section definedby a surface 120 that tapers to a section of reduced diameter defined bysurface 122. From the section of reduced diameter the manifold channelthen expands in diameter in a section defined by surface 124 to anoutlet of the manifold 126 that communicates with the bore of the nozzle20. FIGS. 11 and 12 show the support ring style nozzle similar to FIGS.1-3. However, other types of nozzles may be used such as, for example, athreaded nozzle as shown in FIG. 8.

As stated above, the valve pin is shown in the fully opened position insolid lines. In FIG. 12, flow control is achieved and melt flow reducedby moving the valve pin 41 forward toward the gate thereby reducing thewidth of the control gap 98. Thus, surface 114 approaches surface 120 ofthe manifold to reduce the width of the control gap and reduce the rateof melt flow through the manifold to the gate.

To prevent melt flow from the manifold bore 19, and end the injectioncycle, the valve pin is moved forward so that edge 128 of the valve pin,i.e., where the stem 102 meets the beginning of curved surface 114, willmove past point 130 which is the beginning of surface 122 that definesthe section of reduced diameter of the manifold bore 19. When edge 128extends past point 130 of the manifold bore melt flow is prevented sincethe surface of the valve stem 102 seals with surface 122 of themanifold. The valve pin is shown in dashed lines where edge 128 isforward enough to form a seal with surface 122. At this position,however, the valve pin is not yet closed at the gate. To close the gatethe valve pin moves further forward, with the surface of the stem 102moving further along, and continuing to seal with, surface 122 of themanifold until the end 112 of the valve pin closes with the gate.

In this way, the valve pin does not need to be machined to close thegate and the flow bore 19 of the manifold simultaneously, since stem 102forms a seal with surface 122 before the gate is closed. Further,because the valve pin is closed after the seal is formed in themanifold, the valve pin closure will not create any unwanted pressurespikes. Likewise, when the valve pin is opened at the gate, the end 112of the valve pin will not interfere with melt flow, since once the valvepin is retracted enough to permit melt flow through gap 98, the valvepin end 112 is a predetermined distance from the gate. The valve pincan, for example, travel 6 mm. from the fully open position to where aseal is first created between stem 102 and surface 122, and another 6mm. to close the gate. Thus, the valve pin would have 12 mm. of travel,6 mm. for flow control, and 6 mm. with the flow prevented to close thegate. Of course, the invention is not limited to this range of travelfor the valve pin, and other dimensions can be used.

FIGS. 13-15 show another alternative hot runner system having flowcontrol in which the control of material flow is away from the gate.Like the embodiment shown in FIGS. 11 and 12, the embodiment shown inFIGS. 13-15 also utilizes an extended valve pin design in which thevalve pin closes the gate after completion of material flow. Unlike theembodiment of FIGS. 11 and 12, however, flow control is performed usinga “reverse taper” pin design, similar to the valve pin design shown inFIGS. 1-5.

The valve pin 200 includes a reverse tapered control surface 205 forforming a gap 207 with a surface 209 of the manifold (see FIG. 14). Theaction of displacing the pin 200 away from the gate 211 reduces the sizeof the gap 207. Consequently, the rate of material flow through bores208 and 214 of nozzle 215 and manifold 231, respectively, is reduced,thereby reducing the pressure measured by the pressure transducer 217.Although only one nozzle 215 is shown, manifold 231 supports two or morelike nozzle arrangements shown in FIGS. 13-15, each nozzle for injectinginto a single or multiple cavities.

The valve pin 200 reciprocates by movement of piston 223 disposed in anactuator body 225. This actuator is described in co-pending applicationSer. No. 08/874,962. As disclosed in that application, the use of thisactuator enables easy access to valve pin 200 in that the actuator body225 and piston 223 can be removed from the manifold and valve pin simpleby releasing retaining ring 240.

The reverse closure method offers an advantage over the forward closuremethod shown in FIGS. 6-9, 11 and 12, in that the action of the valvepin 200 moving away from the gate acts to displace material away fromthe gate, thereby assisting in the desired effect of decreasing flowrate and pressure.

In the forward closure method shown in FIGS. 6-9, forward movement ofthe pin is intended to reduce the control gap between the pin and themanifold (or nozzle) bore surface to thereby decrease flow rate andpressure. However, forward movement of the pin also tends to displacematerial toward the gate and into the cavity, thereby increasingpressure, working against the intended action of the pin to restrictflow.

Like the embodiment shown in FIGS. 6-9, and the embodiment shown inFIGS. 11 and 12, movement of the valve pin away from the gate is alsointended to increase the flow rate and pressure. This movement, however,also tends to displace material away from the gate and decreasepressure. Accordingly, although either design can be used, the reversetaper design has been found to give better control stability in trackingthe target pressure.

The embodiment shown in FIGS. 13-15 also includes a tip heater 219disposed about an insert 221 in the nozzle. The tip heater providesextra heat at the gate to keep the material at its processingtemperature. The foregoing tip heater is described in U.S. Pat. No.5,871,786, entitled “Tip Heated Hot Runner Nozzle.” Heat pipes 242 arealso provided to conduct heat uniformly about the injection nozzle 215and to the tip area. Heat pipes such as these are described in U.S. Pat.No. 4,389,002.

FIGS. 13-15 show the valve pin in three different positions. FIG. 13represents the position of the valve pin at the start of an injectioncycle. Generally, an injection cycle includes: 1) an injection periodduring which substantial pressure is applied to the melt stream from theinjection molding machine to inject the material in the mold cavity; 2)a reduction of the pressure from the injection molding machine in whichmelt material is packed into the mold cavity at a relatively constantpressure; and 3) a cooling period in which the pressure decreases tozero and the article in the mold solidifies.

Just prior to the start of injection, tapered control surface 205 is incontact with manifold surface 209 to prevent any material flow. At thestart of injection the pin 200 will be opened to allow material flow. Tostart the injection cycle the valve pin 200 is displaced toward the gateto permit material flow, as shown in FIG. 14. (Note: for someapplications, not all the pins will be opened initially, for some gatespin opening will be varied to sequence the fill into either a singlecavity or multiple cavities). FIG. 15 shows the valve pin at the end ofthe injection cycle after pack. The part is ejected from the mold whilethe pin is in the position shown in FIG. 15.

As in previous embodiments, pin position will be controlled by acontroller 210 based on pressure readings fed to the controller frompressure sensor 217. In a preferred embodiment, the controller is aprogrammable controller, or “PLC,” for example, model number 90-30PLCmanufactured by GE-Fanuc. The controller compares the sensed pressure toa target pressure and adjusts the position of the valve pin via servovalve 212 to track the target pressure, displacing the pin forwardtoward the gate to increase material flow (and pressure) and withdrawingthe pin away from the gate to decrease material flow (and pressure). Ina preferred embodiment, the controller performs this comparison andcontrols pin position according to a PID algorithm. Furthermore, as analternative, valve 212 can also be a high speed proportional valve.

The controller also performs these functions for the other injectionnozzles (not shown) coupled to the manifold 231. Associated with each ofthese nozzles is a valve pin or some type of control valve to controlthe material flow rate, a pressure transducer, an input device forreading the output signal of the pressure transducer, means for signalcomparison and PID calculation (e.g., the controller 210), means forsetting, changing and storing a target profile (e.g., interface 214), anoutput means for controlling a servo valve or proportional valve, and anactuator to move the valve pin. The actuator can be pneumatic, hydraulicor electric. The foregoing components associated with each nozzle tocontrol the flow rate through each nozzle are called a control zone oraxis of control. Instead of a single controller used to control allcontrol zones, alternatively, individual controllers can be used in asingle control zone or group of control zones.

An operator interface 214, for example, a personal computer, is used toprogram a particular target pressure profile into controller 210.Although a personal computer is used, the interface 214 can be anyappropriate graphical or alpha numeric display, and could be directlymounted to the controller. As in previous embodiments, the targetprofile is selected for each nozzle and gate associated therewith bypre-selecting a target profile (preferably including at least parametersfor injection pressure, injection time, pack pressure and pack time),programming the target profile into controller 210, and running theprocess.

In the case of a multicavity application in which different parts arebeing produced in independent cavities associated with each nozzle (a“family tool” mold), it is preferable to create each target profileseparately, since different shaped and sized cavities can have differentprofiles which produce good parts.

For example, in a system having a manifold with four nozzles coupledthereto for injecting into four separate cavities, to create a profilefor a particular nozzle and cavity, three of the four nozzles are shutoff while the target profile is created for the fourth. Three of thefour nozzles are shut off by keeping the valve pins in the positionshown in FIGS. 13 or 15 in which no melt flow is permitted into thecavity.

To create the target profile for the particular nozzle and cavityassociated therewith, the injection molding machine is set at maximuminjection pressure and screw speed, and parameters relating to theinjection pressure, injection time, pack pressure and pack time are seton the controller 210 at values that the molder estimates will generategood parts based on part size, shape, material being used, experience,etc. Injection cycles are run for the selected nozzle and cavity, withalterations being made to the above parameters depending on thecondition of the part being produced. When satisfactory parts areproduced, the profile that produced the satisfactory parts is determinedfor that nozzle and cavity associated therewith.

This process is repeated for all four nozzles (keeping three valve pinsclosed while the selected nozzle is profiled) until target profiles areascertained for each nozzle and cavity associated therewith. Preferably,the acceptable target profiles are stored in computer member, forexample, on a file stored in interface 214 and used by controller 210for production. The process can then be run for all four cavities usingthe four particularized profiles.

Of course, the foregoing process of profile creation is not limited touse with a manifold having four nozzles, but can be used with any numberof nozzles. Furthermore, although it is preferable to profile one nozzleand cavity at a time (while the other nozzles are closed) in a “familytool” mold application, the target profiles can also be created byrunning all nozzles simultaneously, and similarly adjusting each nozzleprofile according the quality of the parts produced. This would bepreferable in an application where all the nozzles are injecting intolike cavities, since the profiles should be similar, if not the same,for each nozzle and cavity associated therewith.

In single cavity applications (where multiple nozzles from a manifoldare injecting into a single cavity), the target profiles would also becreated by running the nozzles at the same time and adjusting theprofiles for each nozzle according to the quality of the part beingproduced. The system can also be simplified without using interface 214,in which each target profile can be stored on a computer readable mediumin controller 210, or the parameters can be set manually on thecontroller.

FIG. 14 shows the pin position in a position that permits material flowduring injection and/or pack. As described above, when the targetprofile calls for an increase in pressure, the controller will cause thevalve pin 200 to move forward to increase gap 207, which increasesmaterial flow, which increases the pressure sensed by pressuretransducer 217. If the injection molding machine is not providingadequate pressure (i.e., greater than the target pressure), however,moving the pin forward will not increase the pressure sensed bytransducer 217 enough to reach the target pressure, and the controllerwill continue to move the pin forward calling for an increase inpressure. This could lead to a loss of control since moving the pinfurther forward will tend to cause the head 227 of the valve pin toclose the gate and attenuate material flow through and about the gate.

Accordingly, to prevent loss of control due to inadequate injectionpressure, the output pressure of the injection molding machine can bemonitored to alert an operator when the pressure drops below aparticular value relative to the target pressure. Alternatively, theforward stroke of the valve pin (from the position in FIG. 13 to theposition in FIG. 14) can be limited during injection and pack. In apreferred embodiment, the pin stroke is limited to approximately 4millimeters. Greater or smaller ranges of pin movement can be useddepending on the application. If adequate injection pressure is not aproblem, neither of these safeguards is necessary.

To prevent the movement of the valve pin too far forward duringinjection and pack several methods can be used. For example, a controllogic performed by the controller 210 can be used in which the outputsignal from the controller to the servo valve is monitored. Based onthis signal, an estimate of the valve pin position is made. If the valvepin position exceeds a desired maximum, for example, 4 millimeters, thenthe forward movement of the pin is halted, or reversed slightly awayfrom the gate. At the end of the injection cycle, the control logic isno longer needed, since the pin is moved to the closed position of FIG.15 and attenuation of flow is no longer a concern. Thus, at the end ofthe pack portion of the injection cycle, a signal is sent to the servovalve to move the pin forward to the closed position of FIG. 15.

Other methods and apparatus for detecting and limiting forwarddisplacement of the valve pin 200 can be used during injection and pack.For example, the pressure at the injection molding machine nozzle can bemeasured to monitor the material pressure supplied to the manifold. Ifthe input pressure to the manifold is less than the target pressure, orless than a specific amount above the target pressure, e.g., 500 p.s.i.,an error message is generated.

Another means for limiting the forward movement of the pin is amechanical or proximity switch which can be used to detect and limit thedisplacement of the valve pin towards the gate instead of the controllogic previously described. The mechanical or proximity switch indicateswhen the pin travels beyond the control range (for example, 4millimeters). If the switch changes state, the direction of the pintravel is halted or reversed slightly to maintain the pin within thedesired range of movement.

Another means for limiting the forward movement of the pin is a positionsensor, for example, a linear voltage differential transformer (LVDT)that is mounted onto the pin shaft to give an output signal proportionalto pin distance traveled. When the output signal indicates that the pintravels beyond the control range, the movement is halted or reversedslightly.

Still another means for limiting the forward movement of the pin is anelectronic actuator. An electronic actuator is used to move the pininstead of the hydraulic or pneumatic actuator shown in FIGS. 13-15. Anexample of a suitable electronic actuator is shown in co-pending U.S.Ser. No. 09/187,974 now U.S. Pat. No. 6,294,122. Using an electronicactuator, the output signal to the servo valve motor can be used toestimate pin position, or an encoder can be added to the motor to givean output signal proportional to pin position. As with previous options,if the pin position travels beyond the control range, then the directionis reversed slightly or the position maintained.

At the end of the pack portion of the injection cycle, the valve pin 200is moved all the way forward to close off the gate as shown in FIG. 15.In the foregoing example, the full stroke of the pin (from the positionin FIG. 13 to the position in FIG. 15) is approximately 12 millimeters.Of course, different ranges of movement can be used depending on theapplication.

The gate remains closed until just prior to the start of the nextinjection cycle when it is opened and moved to the position shown inFIG. 13. While the gate is closed, as shown in FIG. 15, the injectionmolding machine begins plastication for the next injection cycle as thepart is cooled and ejected from the mold.

FIG. 16 shows time versus pressure graphs (235, 237, 239, 241) of thepressure detected by four pressure transducers associated with fournozzles mounted in manifold block 231. The four nozzles aresubstantially similar to the nozzle shown in FIGS. 13-15, and includepressure transducers coupled to the controller 210 in the same manner aspressure transducer 217.

The graphs of FIG. 16(a-d) are generated on the user interface 214 sothat a user can observe the tracking of the actual pressure versus thetarget pressure during the injection cycle in real time, or after thecycle is complete. The four different graphs of FIG. 16 show fourindependent target pressure profiles (“desired”) emulated by the fourindividual nozzles. Different target profiles are desirable to uniformlyfill different sized individual cavities associated with each nozzle, orto uniformly fill different sized sections of a single cavity. Graphssuch as these can be generated with respect to any of the previousembodiments described herein.

The valve pin associated with graph 235 is opened sequentially at 0.5seconds after the valves associated with the other three graphs (237,239 and 241) were opened at 0.00 seconds. Referring back to FIGS. 13-15,just before opening, the valve pins are in the position shown in FIG.13, while at approximately 6.25 seconds at the end of the injectioncycle all four valve pins are in the position shown in FIG. 15. Duringinjection (for example, 0.00 to 1.0 seconds in FIG. 16b) and pack (forexample, 1.0 to 6.25 seconds in FIG. 16b) portions of the graphs, eachvalve pin is controlled to a plurality of positions to alter thepressure sensed by the pressure transducer associated therewith to trackthe target pressure.

Through the user interface 214, target profiles can be designed, andchanges can be made to any of the target profiles using standardwindows-based editing techniques. The profiles are then used bycontroller 210 to control the position of the valve pin. For example,FIG. 17 shows an example of a profile creation and editing screen icon300 generated on interface 214.

Screen icon 300 is generated by a windows-based application performed oninterface 214. Alternatively, this icon could be generated on aninterface associated with controller 210. Screen icon 300 provides auser with the ability to create a new target profile or edit an existingtarget profile for any given nozzle and cavity associated therewith.Screen icon 300 and the profile creation text techniques describedherein are described with reference to FIGS. 13-15, although they areapplicable to all embodiments described herein.

A profile 310 includes (x, y) data pairs, corresponding to time values320 and pressure values 330 which represent the desired pressure sensedby the pressure transducer for the particular nozzle being profiled. Thescreen icon shown in FIG. 17 is shown in a “basic” mode in which alimited group of parameters are entered to generate a profile. Forexample, in the foregoing embodiment, the “basic” mode permits a user toinput start time displayed at 340, maximum fill pressure displayed at350 (also known as injection pressure), the start of pack time displayedat 360, the pack pressure displayed at 370, and the total cycle timedisplayed at 380.

The screen also allows the user to select the particular valve pin theyare controlling displayed at 390, and name the part being moldeddisplayed at 400. Each of these parameters can be adjusted independentlyusing standard windows-based editing techniques such as using a cursorto actuate up/down arrows 410, or by simply typing in values on akeyboard. As these parameters are entered and modified, the profile willbe displayed on a graph 420 according to the parameters selected at thattime.

By clicking on a pull-down menu arrow 391, the user can select differentnozzle valves in order to create, view or edit a profile for theselected nozzle valve and cavity associated therewith. Also, a part name400 can be entered and displayed for each selected nozzle valve.

The newly edited profile can be saved in computer memory individually,or saved as a group of profiles for a group of nozzles that inject intoa particular single or multi-cavity mold. The term “recipe” is used todescribe a group of profiles for a particular mold and the name of theparticular recipe is displayed at 430 on the screen icon.

To create a new profile or edit an existing profile, first the userselects a particular nozzle valve of the group of valves for theparticular recipe group being profiled. The valve selection is displayedat 390. The user inputs an alpha/numeric name to be associated with theprofile being created, for family tool molds this may be called a partname displayed at 400. The user then inputs a time displayed at 340 tospecify when injection starts. A delay can be with particular valve pinsto sequence the opening of the valve pins and the injection of meltmaterial into different gates of a mold.

The user then inputs the fill (injection) pressure displayed at 350. Inthe basic mode, the ramp from zero pressure to max fill pressure is afixed time, for example, 0.3 seconds. The user next inputs the startpack time to indicate when the pack phase of the injection cycle starts.The ramp from the filling phase to the packing phase is also fixed timein the basic mode, for example, 0.3 seconds.

The final parameter is the cycle time which is displayed at 380 in whichthe user specifies when the pack phase (and the injection cycle) ends.The ramp from the pack phase to zero pressure will be instantaneous whena valve pin is used to close the gate, as in the embodiment of FIG. 13,or slower in a thermal gate (see FIG. 1) due to the residual pressure inthe cavity which will decay to zero pressure once the part solidifies inthe mold cavity.

User input buttons 415 through 455 are used to save and load targetprofiles. Button 415 permits the user to close the screen. When thisbutton is clicked, the current group of profiles will take effect forthe recipe being profiled. Cancel button 425 is used to ignore currentprofile changes and revert back to the original profiles and close thescreen. Read Trace button 435 is used to load an existing and savedtarget profile from memory. The profiles can be stored in memorycontained in the interface 215 or the controller 210. Save trace button440 is used to save the current profile. Read group button 445 is usedto load an existing recipe group. Save group button 450 is used to savethe current group of target profiles for a group of nozzle valve pins.The process tuning button 455 allows the user to change the PID settings(for example, the gains) for a particular nozzle valve in a controlzone. Also displayed is a pressure range 465 for the injection moldingapplication.

Button 460 permits the user to toggle to an “advanced” mode profilecreation and editing screen. The advanced profile creation and editingscreen is shown in FIG. 18. The advanced mode allows a greater number ofprofile points to be inserted, edited, or deleted than the basic mode.As in the basic mode, as the profile is changed, the resulting profileis displayed.

The advanced mode offers greater profitability because the user canselect values for individual time and pressure data pairs. As shown inthe graph 420, the profile 470 displayed is not limited to a singlepressure for fill and pack, respectively, as in the basic mode. In theadvanced mode, individual (x, y) data pairs (time and pressure) can beselected anywhere during the injection cycle.

To create and edit a profile using advanced mode, the user can select aplurality of times during the injection cycle (for example 16 differenttimes), and select a pressure value for each selected time. Usingstandard windows-based editing techniques (arrows 475) the user assignsconsecutive points along the profile (displayed at 478), particular timevalues displayed at 480 and particular pressure values displayed at 485.

The next button 490 is used to select the next point on the profile forediting. Prev button 495 is used to select the previous point on theprofile for editing. Delete button 500 is used for deleting thecurrently selected point. When the delete button is used the twoadjacent points will be redrawn showing one straight line segment.

The add button 510 is used to add a new point after the currentlyselected point in which time and pressure values are entered for the newpoint. When the add button is used the two adjacent points will beredrawn showing two segments connecting to the new point.

FIGS. 19-23 show another alternative embodiment of an injection moldingsystem. The system includes a manifold 515 having a plurality of nozzles520 coupled thereto for injecting melt material into a plurality ofcavities 525. Alternatively, the nozzles can also inject into a singlecavity. In FIG. 19, only one nozzle 520 is shown but the followingdescription applies to all nozzles coupled to manifold 515.

As in previous embodiments, each nozzle in the system includes apressure transducer 530 associated therewith for sensing the pressure ofthe melt material in the manifold which thereby gives an indication ofrate of meltflow through nozzle 520 and into cavity 525 with respect toeach injection molding nozzle. Mold cavity 525 is formed by mold halves526 and 527, which are separated to eject the molded part formed incavity 525 after the injection cycle. As in previous embodiments, thepressure transducer can also be located in the nozzle, the manifold, orthe cavity.

As in previous embodiments, a controller 535 receives signals frompressure transducers 530 coupled to each nozzle 520 (only one of whichis shown). The controller 535 controls solenoid valve 540 which controlsthe movement of a piston in actuator 545 which is coupled to and acts toreciprocate the valve pin 550 to open and close gate 555 to cavity 525.

The controller also sends a signal to servo valve 560A which controlsactuator 560 which in turn controls the movement of a ram 565, andfurther controls solenoid valve 570 which is coupled to another actuator575 which controls a valve 580 which is adapted to open and close amanifold channel 585 which leads to nozzle 520. Each injection nozzlecoupled to manifold 515 (not shown) includes the foregoing actuators545, 575 and 560 and ram 565 and solenoid valves 540 and 570 and servovalve 560A associated therewith for controlling flow from each nozzle.

The actuators are mounted in a clamp plate 595 which also includes anopening 600 that receives an inlet bushing 610 threadably mounted to themanifold 515. The inlet bushing 610 receives a nozzle 590 from aninjection molding machine. The injection molding machine can be, forexample, a reciprocating or non-reciprocating extruder. The injectionmolding machine nozzle 590 feeds melt material into the central bushing610 into a central channel 620 which branches off via a plurality ofchannels 585 and 630 (and others not shown) to a corresponding pluralityof injection molding nozzles 520.

The foregoing embodiment is similar to previous embodiments in thatpressure transducer 530 is used to measure pressure indicative of flowrate of melt material into cavity 525 during the injection cycle. (Theactuators described herein are hydraulic actuators, however, pneumaticor electric or other types of actuation can also be used.) Also, as inprevious embodiments, a controller 535 compares the pressure sensed bythe pressure transducer to target values of a target profile and issuescontrol signals to increase or decrease pressure to track the targetprofile for each nozzle.

In previous embodiments the controller controlled the position of avalve pin to regulate flow rate independently at each gate duringinjection. The foregoing embodiment also enables the flow rate ofplastic to be controlled independently through each nozzle 520 and eachgate during injection. However, in the embodiment shown in FIGS. 19-23,a valve pin is not used to control flow rate as in previous embodiments.Rather, valve pin 550 is used only to open and close gate 555.

In the foregoing embodiment, ram 565 and well 640 are used to regulatethe flow of melt material through nozzle 520 and into cavity 525 in thefollowing manner.

At the start of the injection cycle, valve gate 555 is closed by valvepin 550 and valve 580 is opened to permit flow through manifold channel585 (see FIG. 20). The injection molding machine nozzle 590 injects meltmaterial through the inlet bushing 610 into the manifold 515, such thatit fills well 640 (see FIG. 20). The valve pin 550 is still in theclosed position while the well 640 is being filled. Ram 565 is in apredetermined adjustable retracted position to permit a specific volumeof melt material to gather in well 640 (see FIG. 21). FIG. 21 shows thesystem ready to inject melt material into cavity 525.

The controller 535 then signals the servo valve 540 to cause actuator545 to retract valve pin 550 and open gate 555, while also signalingservo valve 570 to cause actuator 575 to close valve 580 and shut offmanifold channel 585. Closing valve 580 when injecting into the cavityprevents backflow of material through channel 585. This position isshown in FIG. 22.

The controller then signals actuator 560 to move ram 565 forward toinject material from the well 640 through the nozzle 520 and into thecavity 525. During this time, the controller controls the velocity atwhich the ram moves forward, according to the pressure sensed bypressure transducer 530, in relation to a target pressure profile.Accordingly, if the pressure transducer 530 senses a pressure that isbelow the target pressure for that particular time during the injectioncycle, the controller 535 signals the actuator 560 to increase thevelocity of the ram 565, conversely, if the pressure sensed is greaterthan the target pressure, the controller will control the actuator todecrease the velocity of the ram forward. When the ram reaches itslowermost position, the cavity 525 is full and the gate is closed (seeFIG. 23). Alternatively, ram 565 can be velocity controlled by using alinear transducer to monitor ram position. If so, at the end ofinjection, the ram is not bottomed out, and control can be transferredto the pressure transducer 530 during pack.

As stated above, a reciprocating or non-reciprocating extruder can beused. If a non-reciprocating extruder is used, plastication into themanifold can be continuous, and the valve 580 is used to shut off themanifold channel 585 during injection so that during this time noplastic can flow through the manifold channel. When well 640 is filledwith melt material, plastication in the non-reciprocating extruder canbe stopped until the next cycle.

As in previous embodiments described herein, preferably a PID algorithmis used to control the actuator 560 to track the target profile. Thetarget profile can be created in the same manner as described above withrespect to previous embodiments.

Using the embodiment shown in FIGS. 19-23, the flow rate of plasticthrough each gate is controlled independently. Additionally, the use ofwell 640 enables one to control the specific volume of plastic injectedinto each cavity 525, which leads to part-to-part consistency,especially when molding in multi-cavity applications in which eachcavity 525 is an identical part. By altering the position of ram 565when injecting melt material into well 640, the volume of material inwell 640 can be controlled, thereby controlling the volume of materialinto cavity 525.

FIGS. 24-28 show an alternative embodiment in which a load cell 140 isused to sense the melt pressure acting on the face 142 of valve pin 41.Where possible, reference characters are used that refer to elementscommon to FIG. 1. As in previous embodiments, an actuator 49 is used totranslate the valve pin 41 toward and away from the gate. The actuator49 includes a housing 144 and a piston 146 slidably mounted within thehousing. The actuator is fed by pneumatic or hydraulic lines 148 and150. Other actuators, for example, electrical actuators may also beused.

The valve pin 41 is mounted to the piston 146 so that valve pintranslates through the injection nozzle 23 with movement of the piston.The valve pin is mounted to the piston via a pin 152. The pin 152 isslotted so that a clearance 154 exists in which the valve pin cantranslate with respect to the pin 152 and piston 146. The valve pinbears against a button 156 on the load cell 140. The load cell 140 ismounted via screws 158 to the piston. Thus, as shown in FIG. 26, a forceF2 acting on the valve pin will cause the load button 156 to depress.Excitation voltages or other types of signals which indicate theproportionate force on the load button 156 are carried through cable 160and fed to a controller 151.

In operation, as seen in FIG. 24, the melt material is injected from aninjection molding machine nozzle 11 into an extended inlet 13 mounted toa manifold 15 through respective injection molding nozzles 21 and 23 andinto mold cavities 162 and 164. In the embodiment shown, a multi-cavitymold is shown in which nozzles 21 and 23 inject melt material to formdifferent size molded parts in cavities 162 and 164, respectively. Asstated above with respect to the embodiment shown in FIG. 1, a moldcavity with multiple gates can be used, or multiple mold cavities withcavities having the same size can be used.

When the valve pin 41 is retracted to permit melt material to beinjected into the cavity 162, the melt pressure will act on the face ofthe valve pin 142 with the resulting force being transmitted through theshaft of the valve pin to the load sensor 140 (see FIGS. 26-27). Thus,the load (F2) sensed by load cell 140 is directly related to the meltflow rate into the melt cavity.

Sheer stresses caused by the melt streaming downward over the valve pinwill tend to reduce the pressure sensed by the load cell but suchstresses are typically less than the nominal load due to the meltpressure. Thus, the resultant force F2 will tend to compress the valvepin toward the load cell, with the possible exception of the initialopening of the valve, and the load cell provides an accurate indicatorof the melt pressure at the gate. If the application results in sheerstresses exceeding F2, the load cell can be pre-loaded to compensate forsuch stresses.

Similar to previous embodiments described above, the signal transmittedthrough cable 160 is compared by controller 151 with a target value of atarget profile and the controller adjusts the position of the valve pinaccordingly to increase or decrease flow rate. In this embodiment, thetarget profile is also a time versus pressure profile, but the pressureis the a result of the force of the pin on the load cell, as opposed toprevious embodiments in which a pressure transducer directly senses theforce of the flow of the melt material. The profile is created insimilar fashion to the embodiments described above: running the processand adjusting the profile until acceptable parts are produced.

The valve pin controls the flow rate through the gate using a taperededge 155 to form a control gap 153 close to the gate. It should benoted, however, that any of the other valve pin designs described hereincan be used with the load cell 140. Accordingly, when the pressuresensed by the load cell is less than the target pressure on the targetprofile, the controller 151 signals the actuator to retract the valvepin to increase the size of the control gap 153 and, consequently, theflow rate. If the pressure sensed by the load cell 140 is greater thanthe target pressure, the controller 151 signals the actuator to displacethe valve pin toward the gate to decrease the size of the control gap153 and consequently, the flow rate.

The use of the load cell has an additional application shown in FIG.27A. In a single cavity multiple gate system it is often desirable toopen gates in a cascading fashion as soon as the flow front of the meltmaterial reaches the gate. When melt material 166 has flowed into thegate area of the valve pin, a force F3 from the melt in the cavity isexerted on the face 142 of the valve pin.

In this way, gates can be sequentially opened in cascading fashion bysensing the force of the melt pressure on the face of the valve pin whenthe valve pin is closed. Given typical gate diameters of 0.2 inches andmelt pressures of 10,000 psi, the resulting force of 300 pounds isreadily measured by available load sensors, since the force of the cellequals the area of the gate times the pressure at the gate. Thus, thismelt detection can then be used to signal the opening of the gate as inthe sequential valve gate. This assures that the gate does not openprematurely.

FIGS. 28A and 28B show an alternative embodiment in which the sheerstress on the valve pin is reduced. The nozzle 21 is designed to includea channel for melt flow 168 and a bore 170 through which the valve pinreciprocates. As such, the flow does not cause any axial sheer stress onthe valve pin and thus reduces errors in pressure sensing. An indent 172is provided in the nozzle 21 so that side load on the valve pin isreduced, i.e., to equalize pressure on both sides of the valve pin. Anadditional benefit to the configuration shown in FIGS. 28A and 28B isthat since the flow of material is away from the valve pin, the valvepin does not “split” the flow of material, which can tend to cause partlines or a flow streak on the molded part.

FIG. 29 shows another alternative embodiment of the present inventionsimilar to FIG. 19. As in FIG. 19, a ram 565 is used to force materialfrom well 640 into cavity 525 at a controlled rate. The rate iscontrolled by signals sent from controller 535 to servo valve 560A,which in turn controls the velocity at which actuator 560 moves ram 565forward.

In FIG. 29, actuator 560 is shown in more detail including piston 564,actuator chamber 566, and hydraulic lines 561 and 562 controlled byservo valve 560A. Energizing hydraulic line 561 and filling chamber 566causes piston 564 and ram 565 to move forward and displace material fromwell 640 through channel 585 and nozzle 520, and into cavity 525.

In the embodiment of FIG. 19, the controller controls the rate at whichthe ram injects material according to signals received by pressuretransducer 530, compared to a target profile. In the embodiment of FIG.29, pressure transducer 530 has been removed in favor of pressuretransducer 563 mounted along hydraulic line 561 which leads to chamber566. The pressure transducer 560 senses the hydraulic fluid pressure inline 561 and sends a proportional signal to the controller 535. Sincethe pressure of the hydraulic fluid entering chamber 566 is directlyrelated to the rate at which the ram 565 moves forward, and the rate atwhich the ram moves forward is directly related to the rate of materialflow into the cavity 525, the pressure sensed by pressure transducer 560is directly related to the rate of material flow into the cavity 525,and can be used to control the material flow rate.

Accordingly, as in previous embodiments, a target profile is createdthat has been demonstrated to generate acceptable molded parts. In theembodiment of FIG. 29, however, the target profile represents targetvalues of the hydraulic pressure sensed by pressure transducer 563, asopposed to directly sensing the material pressure. In operation, thecontroller compares the pressure signal sensed from pressure transducer563 to the target pressure profile for gate 555. If the pressure sensedis too low, the controller will increase the hydraulic pressure in line561 (which increases the velocity of the ram which increases flow rateof the material), if the pressure is too high the controller willdecrease the hydraulic pressure (which decreases the velocity of the ramwhich decreases the rate of material flow).

The target pressure profile of the hydraulic fluid will appear similarto a conventional material profile, since the pressure of the hydraulicfluid will rise rapidly during the injection portion of the cycle, leveloff during the pack portion of the cycle, and go to zero pressure ascycle ends the valve pin 550 closes.

Although only one injection nozzle 520 and cavity 525 is shown, there isa like arrangement associated with each injection nozzle of actuators575, 565, 545, as well as solenoid valves 540 and 570 and servo valve560, to independently control the melt flowing from each gate, accordingto the target profile created for that gate. Also, although a singlecavity 525 is shown, each nozzle may inject to multiple cavities or asingle cavity mold. Only a single controller 535, however, is needed tocontrol all the nozzles associated with manifold 515.

Using the foregoing arrangement of FIG. 29, as in previous embodiments,the material flow from each nozzle of the manifold can be controlledindependently.

FIG. 30 shows another alternative embodiment of the present invention.The embodiment of FIG. 30 is substantially the same as the embodimentshown in FIG. 13 with the exception that pressure transducer 217 hasbeen moved from manifold 231 to inside the mold half 650 which, togetherwith mold half 660, forms mold cavity 670 in which the molded part isformed. Accordingly, in this embodiment, the target profile representstarget values of the pressure sensed by pressure transducer 217 insidethe cavity opposite the gate 211.

The operation of the embodiment of FIG. 30 is the same as that describedin the embodiment shown in FIG. 13 in terms of target profile creationand use of valve pin 200 to control the material flow (interface 214 isnot shown FIG. 30 but can be used). However, placing the pressuretransducer in the cavity offers several advantages, for example, in thecavity the pressure transducer 217 is not exposed to the hightemperatures generated by the manifold, as in FIG. 13. Also, thepresence of the pressure transducer in the manifold may slightly disruptmaterial flow in the manifold. Another consideration in choosing whetherto mount the transducer in the mold or in the manifold is whether themold geometry permits the transducer to be mounted in the mold.

FIG. 31 is another alternative embodiment of the present invention thatis similar to FIG. 13 (like reference characters are used whereverpossible). Target profile creation as well as the flow control operationby valve pin 200 is substantially the same as described above. FIG. 31,however, does not include a pressure transducer 217 as shown in FIG. 13to directly sense the flow of melt material into the cavity. Rather,similar to the embodiment shown in FIG. 24, the arrangement shown inFIG. 31 performs flow control by sensing the material pressure F2exerted by the melt material on the valve pin.

In FIG. 24 measuring the load on the valve pin was performed using aload cell 140, however, in FIG. 31, it is performed by pressuretransducers 700 and 710 mounted along hydraulic lines 720 and 730 whichlead to actuator chambers 740 and 750, respectively. Energizing lines720 and 730 and filling actuator chambers 740 and 750, enables axialmovement of piston 223, thereby moving valve pin 200 and affecting theflow rate of the material into the cavity 760 as described above.

Pressure transducers 700 and 710 sense a differential pressure which isdirectly related to the force exerted on valve pin 200, which isdirectly related to the flow rate of the material. For example, when thematerial flow causes a force F2 to act on valve pin 200, the forcerelates up the valve pin to the piston, which in turn tends to increasethe pressure in chamber 740 and line 720 and decrease the pressure inchamber 750 and line 730, directly causing a change in the difference inthe pressures sensed by the transducers 700 and 710. Accordingly, thedifferential pressure is directly related to the flow rate of thematerial into the cavity.

Once an acceptable target profile of differential pressure is developedusing techniques described above, the controller will cause the servovalve 212 to track this target profile by altering the position of thevalve pin to change the flow rate of the material and track thedifferential pressure target profile. For example, if the differentialpressure is too high (e.g., the pressure sensed by transducer 700 ishigher than the pressure sensed by transducer 710 by an amount greaterthan the target differential pressure) the controller will cause servovalve to retract the valve pin to reduce the flow rate, thereby reducingthe force F2 on the valve pin, thereby decreasing the pressure inchamber 740 and line 720, thereby decreasing the pressure sensed bytransducer 700, thereby decreasing the difference in pressure sensed bytransducers 700 and 710. Note, in certain applications the differentialpressure may be negative due to the sheer force of the material on thevalve pin, this however will not affect the controller's ability totrack the target profile.

As in the embodiment shown in FIG. 24, the embodiment shown in FIG. 31offers the advantage that it is not necessary to mount a pressuretransducer in the mold or the manifold. As in all previous embodiments,the embodiment shown in FIG. 31 enables the material flow from eachnozzle attached to the manifold to be independently profileable.

Having thus described certain embodiments of the present invention,various alterations, modifications, and improvements will readily occurto those skilled in the art. Such alterations, modifications, andimprovements are intended to be within the spirit and scope of theinvention. Accordingly, the foregoing description is by way of exampleonly, and not intended to be limiting. The invention is limited only asdefined in the following claims and the equivalents thereof.

What is claimed is:
 1. An injection molding apparatus comprising: amanifold; at least one injection nozzle coupled to the manifold; anactuator; and a valve pin adapted to reciprocate through the manifoldand the injection nozzle, the valve pin having a first end coupled tothe actuator, a second end that closes the gate in a forward position,and a control surface intermediate said first and second ends foradjusting the rate of material flow during an injection cycle, whereinretracting the valve pin tends to decrease the rate of material flowduring the injection cycle and displacing the valve pin toward the gatetends to increase the rate of material flow during the injection cycle.2. The injection molding apparatus of claim 1, wherein the controlsurface forms a gap with a surface of the manifold so that the size ofthe gap is decreased when the valve pin is retracted away from the gateand the size of the gap is increased when the valve pin is displacedtoward the gate.
 3. The injection molding apparatus of claim 1, furthercomprising a controller coupled to the actuator to adjust the valve pinto a plurality of positions during the injection cycle to alter the rateof material flow during the injection cycle.
 4. The injection moldingapparatus of claim 3, wherein the controller compares a sensed conditionrelated to material flow rate to a target condition and adjusts thevalve pin to track the target condition.
 5. The injection moldingapparatus of claim 4, wherein the sensed condition is pressure, and theapparatus further comprises a pressure transducer for sensing thematerial pressure downstream the control surface of the valve pin. 6.The injection molding apparatus of claim 5, wherein the pressuretransducer is coupled to one of the manifold, the injection nozzle andthe mold cavity.
 7. The injection molding apparatus of claim 1, furthercomprising means for limiting the forward movement of the valve pinduring the injection cycle.